package practice;

import java.util.Scanner;

public class Day8 {
    /**
     * 卒过河问题（典型的dp问题）
     * @param args
     */
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int m = in.nextInt();
        int x = in.nextInt();
        int y = in.nextInt();
        long[][] dp = new long[n+2][m+2];
        x += 1;
        y += 1;
        dp[0][1] = 1;
        for(int i = 1; i <= n + 1; i++) {
            for(int j = 1; j <= m + 1; j++) {
                if(i != x && j != y && (Math.abs(i-x) + Math.abs(j-y)) == 3 || (i == x && j == y)) {
                    dp[i][j] = 0;
                }else {
                    dp[i][j] = dp[i][j-1] + dp[i-1][j];
                }
            }
        }
        System.out.println(dp[n+1][m+1]);
    }
}
